噴射混凝土巷道應(yīng)力測量儀的性能外文文獻翻譯中英文翻譯

1、英文原文The performance of pressure cells for sprayed concrete tunnel liningsC . R . I . C L AY TO N,J. P. VA N D E R B E R G , G . H E Y M A N N, A . V. D. B I C Aan d V. S . H O P EAbstract: The paper examines the factors that affect the performance of tangential cells embedded in shotcrete tunnel lin

2、ings. Newdata, derived from fi eld monitoring, numerical modelling,and calibration tests carried out to simulate the embedment and crimping processes, are presented. These suggest that although well-designed embedded total pressure cells will have cell action factors close to unity, they cannot be a

3、ssumed to provide reasonable estimatesof the stresses within sprayed concrete linings, unless the infl uences of installation effects, temperature changes, shrinkage and subsequentcrimping can be taken into account.Keywords: fi eld instrumentation; tunnels.IntroductionThe pressure cells used for mea

4、suring the compressive stressesin shotcrete tunnel linings generally consist of two stainle ss steel plates with a thin fl uid- fi lled cavity between them. The cavity is connected either to a membrane-type bypass valve or to a vibrating-wire pressure transducer. The use of other direct-stress instr

5、uments has been reported in the literature, althoughinfrequently. Pressure cells are typically installed in one of two orientations: radial, to record the stress between the sprayed concrete and the ground surrounding the tunnel; and tangential, to record the hoop stress within the tunnel lining its

6、elf. This paper considersonly tangential cells. Despite their widespread use in practice, there has been verytle research reported in the literature on the use and behaviourof shotcrete pressure cells.Many practitioners remain doubtful of the ability of embedded pressure cells to measure the actual

7、stresses in concrete tunnellinings. In a previous paper reviewing instrumentation for sprayed concrete lined tunnels the present authors noted some of the potential diffi culties, stating that it was 'extremely unlikely that embedded cells be used for monitoring the actual stress in a tunnel lin

8、ing' . Yet, potentially, pressure cells are a valuable source of information that might be used to assesswhether tunnel design assumptions are justii ed, and this paper therefore reports the ndings of our further research into this important topic.Factors affecting the pressures recorded byangen

9、tial pressure cells intunnel liningsDirect stress measurement within any medium is made difficult by the many factors that can affect the results. In the case of tangential pressure cells embedded in shotcrete our recent experiencesduring tunnel monitoring suggest that these are as follows.Cell prop

10、ertiesThe cell should be constructed so that the stressesin the shotcrete are not significantly modified by its presence. Since the compressibility of the fluid in the cell is less than the surrounding materials it will under-read, but this can largely be compensatedfor by making the cell wide and t

11、hin. The use of cell fluids such as mercury or oil will affect not only the compressibility of cells but also their temperature sensitivity. Changes in temperature will expand the fluid against the surrounding, relatively rigid cell metal and surrounding concrete, and will produce a change in measur

12、ed stress.Installation effectsThe inadvertent formation of cavities around the cell during shotcreting will lead to a soft measurement system, which will subsequently under-read. Incorrect positioning of the cell within the lining, rotating it towards the radial direction, can also cause it to under

13、-read somewhat, because radial stresses are typically less than 10% of tangential. Indeed the actual thickness of the lining at the point of installation will also affect the interpretation of the stress measurements.Post-installation factorsAs noted above, temperature changes can be expected to lea

14、d to changes in measured stresses. Shrinkage during the early life of the shotcrete will result in changes in the recorded stress that are not due to external stress changes. Crimping, which is often undertaken to ensure that pressure cells are properly bedded within the shotcrete , can provide a si

15、gnificant offset to the measured pressures.Numerical and physical experiments, and results from monitoringNumerical modelling and physical simulation have been carried out to assess the actual performance of some stress cells used in practice, and to place their performance in the context of other c

16、ell designs.Numerical modelling to assess the effects of cell fluidTo examine the effect of cell fluid on cell performance two idealised circular cells embedded in a block of concrete were modelled under axisymmetric conditions using the finite element package LUSAS. The geometry of the cells and th

17、e material properties modelled are shown in Fig. 1. The 160 mm diameter cell is somewhat larger than many of the cells currently in use, whereas the 80 mm cell is smaller, and was considered by the authors to be likely to have an excessive T/D ratio. In the first numerical experiment the effect of t

18、he bulk modulus of the cell fluid wasinvestigated, by applying a constant external axial stress and varying the cell cavity pressure . The bulk modulus equivalent to each cell action factor was calculated by integrating the displacementsalong the surface of the cell cavity. Fig. 2 shows the consider

19、able influence of bulk modulus on cell action factor, but it also shows that when reasonable cell geometries are used cell action factors remain tolerably close to unity when oil is substituted for mercury.80 mm or IGO mm d tameterCavity! A ppi ed vertical sttessUI山山l山山山uwPressure cell；/Concrete800

20、m mLlslfif ia lV IPCoiicr &I&300000253 0 x 1O 3S till包teel21 OOOOO 28A S X TO .(c)Fig. 1. Geometry of cells and properties of materials used during numerical modelling: (a) idealised pressure cell; (b) geometry modelled; (c) material propertiesBu k modulus of cell fluid : MPaFig. 2. Effect o

21、f bulk modulus of cell fluid on cell action factorPhysical simulationCalibration tests were conducted to evaluate the performance of the vibrating-wire mercury-filled pressure cells, in three phases:(a) During the first phase the manufacturer's calibration of the pressure cells was checked by co

22、nducting an air pressure calibration on all the cells used.This was done in a 1 m diameter chamber, in the laboratory.(b) The second phase of the experimental work was conducted to investigate whether tangential cells installed under ideal and controlled conditions could produce reliable results. Th

23、is was done by installing two pressure cells in a precast concrete slab, constructed in the laboratory.(c) The final phase of the experimental work was designed to investigate the performance of the tangential cells under 'working conditions', as well as to investigate ways of installing the

24、 cells to improve their performance. This was done by installing tangential pressure cells in shotcrete slabs, formed in a tunnel under working conditions.The cells used for the experimental work were mercury-filled vibrating-wire cells supplied by Geokon, and with a full-scale range of 20 MPa (Fig.

25、 3). All the pressure measurements were calculated using the temperature correction supplied by the manufacturer.Fig. 3. Vibrating-wire mercury-filled concrete stress cellThe second phase of the calibration testing was carried out to investigate the performance of the tangential pressure cells under

26、 ideal and controlled conditions. For this experiment two cells were embedded in a 25 MPa ready-mix concrete slab, 1.0 m high, 1.0 m wide and 0.3 m thick. The two cells were tied to a cage constructed from reinforcing bar meshes, which were identical to those in use in the Heathrow Terminal 4 statio

27、n tunnels. The experimental set-up is shown in Fig. 4, except that in the first set of experiments two bare cells were used. One bare cell and one precast cell were used in a subsequent experiment, described later in this paper.Direction of load ingFig. 4. Layout of cells embedded in concrete panelD

28、uring the curing period the slab temperature increased to about 32 C, and afterwards decreased slowly over several days. Monitoring was carried out until the cell temperatures reached equilibrium with the laboratory environment (Fig. 5).3020O24681O 1214Elapsed tnne: daysFig. 5. Temperatures measured

29、 after casting cells in ready-mixed concreteOAt each load increment the cell readings were observed tstabilise rapidly: creep effects were not apparent. The value ofcell action factor was subsequently calculated from pressure cell readings and average applied vertical stresses .The fi nal phase of t

30、he experimental work consisted of the evaluation of the tangential pressure cells installed under 'working conditions'. This was done by placing two pressure cells in each of two slabs, similar to the above but constructed using shotcrete in a tunnel at Heathrow Terminal 4. Because the resul

31、ts of the experiment on the cells installed in the concrete slab showed that under ideal conditions the cells seem to perform satisfactorily, it was argued that failure under working conditions might result from installation effects. A major dif fi culty with the installation of tangential pressure

32、cells is ensuring that no voids are formed in'shadow zones' around the cellduring shotcreting. It was therefore decided to precast one of the cells in each of the two slabs in a tapered concrete block, designed to prevent the formation of shadow zones (Fig. 6).Fig. 6. Detail of cell cast in

33、precast concretecellDiscussionTheoretical considerations suggest that a well-designed embedded cell, with high stiffness and a low aspect ratio (T/ D), should have a cell action factor close to unity. Our experiments on commercially available cells support this view. The ability of a cell to measure

34、 the applied pressure correctly is dependent upon additional factors, however. Offsets due to temperature, crimping and shrinkage must be properly taken into account. The quality of cell installation must be assessed.Although manufacturers routinely supply temperature correction factors for vibratin

35、g-wire cells, these correct for the sensitivity of the transducer alone. For a 160 mm radial cell fi lled with mercury the authors' numerical modelling results suggest that a temperature change of 20 C will produce a pressure change of the order of 2 MPa. Oil-fi lled cells can be expected to be

36、more temperature sensitive. A 20 C temperature change might produce about a 3 MPa pressure increase, whichis of the same order as the tangential stress found in manyompleted shotcrete tunnel linings.To the authors' knowledge, no estimates of the increase in measured stress induced by shrinkage h

37、ave ever been reported in the literature. In order to make an initial estimate the data from the authors' laboratory experiments were reprocessed, using only those data obtained when the concrete slabs werenloaded.If crimping is carried out then the zero offset of the cell is permanently altered

38、. In a real installation the absolute pressure can be recovered only if the pressure change during crimping is carefully recorded. It is suggested that, although crimping is unnecessary if cells are well-designed and installation is good, the initial gradient of the crimping curve should provide a g

39、ood guide to the cell action factor of the installed cell, with high crimping gradients indicating satisfactory cells. The pressure increases caused by crimping can be eliminated by subtracting them from the values subsequently recordedConclusionsUsing numerical and physical experiments, coupled wit

40、h field observations, this paper has for the first time attempted a rational assessment of the many factors that may lead to embedded shotcrete pressure cells misreading.The data suggest that, unless installation defects are present, the cell action factors of well-designed shotcrete pressure cells

41、are likely to be near to 1. However, other factors need to be taken into account before embedded pressure cell data can be used to determine the true stress in a tunnel lining. Temperature changes immediately after cell placement will be large, and, coupled with the high rate of shrinkage that occur

42、s during the early life of shotcrete, will prevent satisfactory stress measurement during this period. Seasonal temperature changes will cause further changes in pressure cell readings. Strains due to shrinkage of the shotcrete mayalso significantly increase the measured stresses. Our data suggest t

43、hat it is possible to predict the temperature sensitivity of the shell/shotcrete system using numerical modelling. Field data, laboratory measurement and estimates based upon an analytical approach are in good agreement.After temperature changes due to cement hydration have ceased, the shape of the

44、crimping curve can be used to assessthe quality of cell installation. However, the crimping procedure will generate offset pressuresthat may be of the same order of magnitude as the actual pressure to be measured in most shotcrete linings. Measurements made after the crimping procedure is completed

45、must be corrected by subtracting the pressure increase observed during crimping. If shadow zones cannot be prevented during installation then the use of precast cells may be advantageous, although the cell action factor of the installation will be modified.The various factors influencing the measure

46、ment of the absolute stress in a shotcrete lining cannot be taken account of when routinely interpreting pressure cell data, without the benefit of careful calibration, numerical estimates of thermal sensitivity, and experimental determinations of the effects of shrinkage. We have shown that the eff

47、ects of temperature, shrinkage and crimping will probably be large, and of the order of the stresses tobe measured. However, the cell action factors of well-designed and well-installed pressure cells will be close to unity and, as we have shown, it should be possible to take account of the effects o

48、f temperature changes and shrinkage, to estimate the quality of the installation, and to correct forcrimping offset. Despite the potential difficulties the authors believe that tangential pressure cells can still be useful in many tunnelling applications, but only provided great care is taken in the

49、 interpretation of their measurements.AcknowledgementsThe authors gratefully acknowledge the support of Heathrow Express, Mott MacDonald Consulting Engineers, and the Engineering and Physical Sciences Research Council of the UK, and the help of Mr J. Barrie Sellers, President of Geokon, Inc.,USA, in

50、 reviewing the manuscript. The work described in this paper forms part of a wider research programme now being carried out by the University of Southampton, UK, into the behaviour of SCL tunnels.中文譯文噴射混凝土巷道應(yīng)力測量儀的性能C.R.I.克萊頓，J.P.范德伯格，G.霍曼，A.V.D.哈曼和V.S.霍普摘要：本文研究了影響噴射混凝土巷道應(yīng)力測量儀性能的因素。 新數(shù)據(jù)通過實地 檢測、數(shù)字模擬、模擬

51、埋設(shè)標定試驗和褶曲變化進程等進行派生的表達。 這些數(shù) 據(jù)表明，雖然精心設(shè)計的應(yīng)力測量儀測出的數(shù)據(jù)很接近圍巖整體運動規(guī)律， 但是 它們不能被假定為對噴射混凝土巷道圍巖應(yīng)力提供了合理的估計， 除非將安裝影 響、溫度變化、圍巖收縮及后續(xù)的褶曲變化等因素考慮在內(nèi)。關(guān)鍵詞：實地檢測；巷道1前言用來測量噴射混凝土巷道壓縮應(yīng)力的應(yīng)力測量儀 （以后簡稱測力儀）通常由 兩個不銹鋼板組成，兩個板之間有一個充滿液體的管。這個管一般和一個膜式旁 路閥門或一個弦式壓力傳感器連接。 在文獻中，也提到了一些其他測量應(yīng)力的器 材的作用，雖然不常見。測力儀通常安裝在兩個方向之一：徑向，記錄噴射的混 凝土與巷道圍巖之間的應(yīng)力；切

52、向，記錄巷道內(nèi)的切應(yīng)力。本文認為只有切向應(yīng) 力。雖然它們在實踐中廣泛使用，但在研究報告文獻中很少有介紹噴射混凝土巷 道測力儀的使用和作用。很多學者仍然保留著對嵌入式測力儀能夠測量噴射混凝 土巷道實際應(yīng)力的性能的懷疑。在前一篇審查噴射混凝土巷道測力儀性能的文章 中，作者指出了一些潛在困難，特別說明嵌入式測力儀用于監(jiān)測巷道實際應(yīng)力是 極不可能的。然而，潛在的測力儀是一種寶貴的信息， 可能被用來評估巷道設(shè)計 假設(shè)是否合理，因此，這篇文章在這個重要的項目中報告了我們進一步研究的成 果。2切向測力儀測量巷道應(yīng)力的影響因素由于很多因素可以影響結(jié)果，所以在任何媒體中直接測量都很困難。 在切向 測力儀嵌入混凝

53、土的情況下，在巷道監(jiān)測過程中，我們最近的經(jīng)驗表明如下所示。 2.1測力儀特性測力儀應(yīng)該被改進，以便巷道中的壓力不會被它的存在而受到明顯改變。當 測力儀中的流體的可壓縮性小于周圍材料， 它會讀不出數(shù)據(jù)，但這可以在很大程 度上通過將測力儀變寬變長的方法來彌補。測力儀中的流體（如汞或油）的使用 不僅會影響測力儀的可壓縮性，而且會影響他們的溫度敏感性。溫度的變化將促 使流體對抗環(huán)境、相對剛性的測力儀金屬和周圍的混凝土， 并且會使測量的應(yīng)力 產(chǎn)生變化。2.2 安裝影響噴漿過程中，在測力儀周圍無意形成的空隙會導致一個松軟的測量環(huán)境， 這 就會使測量儀讀不出數(shù)據(jù)。不正確安裝的測量儀，旋轉(zhuǎn)它往徑向，有時也會導

54、致 讀不出數(shù)據(jù)，這是因為徑向應(yīng)力一般比切向應(yīng)力小 10%0事實上，實際安裝時的 襯砌厚度也會影響應(yīng)力測量的結(jié)果。2.3 安裝后的影響因素如上所述，溫度的變化將會導致實測應(yīng)力變化。 早期噴漿中的收縮過程導致 應(yīng)力記錄的變化不取決于外部應(yīng)力的變化。經(jīng)常進行褶曲以確保測力儀正常嵌入 巷道內(nèi)，可以提供一個明顯的偏移測量應(yīng)力。3數(shù)字模擬與物理實驗和檢測結(jié)果數(shù)字和物理模擬實驗已進行，用來評估一些測力儀在實踐中的性能， 并且將 這些性能用于一些其它測力儀的設(shè)計中去。3.1 數(shù)字模擬實驗評估壓力計流體的影響為了檢驗測力儀中流體對測力儀性能的影響，參照實驗一一將兩個圓形測力 儀以軸對稱方式嵌入混凝土塊中，使用有

55、限元包LUSAS進行測定。測力儀的幾何結(jié)構(gòu)和材料屬性參照圖如圖1所示。160毫米直徑的測力儀比許多目前正使用 的測力儀要大一點，而80毫米直徑的要小一點，作者認為可能是 T/D比較大。 在第一個數(shù)字模擬實驗中，通過應(yīng)用一個恒定的外部軸向應(yīng)力和不同的測力儀管 內(nèi)應(yīng)力，調(diào)查了測力儀流體體積彈性模量的影響。 體積彈性模量相當于通過整體 的測力儀管曲面位移計算每一個應(yīng)力單元。 圖2顯示了應(yīng)力變化因素體積彈性模 量的相當大的影響力，但同時還顯示了當應(yīng)用合理的幾何形狀時， 在用汞替代油 的情況下，應(yīng)力單元變化情況仍和整體一致。無非力輛制側(cè)方忙潦體首BClmtr芭1F，口 e而直徑 I提ft的任冏應(yīng)力uiu

56、uiuiuuuuuuwni碗土1m用巾并中把tffffrn憎6OObd材料E/MF&V小C柳土300000.250 003無張力鋼210D00Q 260.0046圖2測力儀流體體積彈性模量的影響因素3.2 物理模擬實驗用來評估弦式汞應(yīng)力測力儀性能的校準測試分為三個階段：1）在第一階段，通過對所有使用的測力儀進行一個空氣壓力試驗來檢查制造商校準過的測力儀。這個實驗是在實驗室中一個1米直徑的空間中進行的。2）實驗工作的第二階段是研究測力儀在理想和能控制的條件下安裝，到底 哪個能得出可靠的結(jié)果。這通過在實驗室中構(gòu)建的預(yù)制混凝土板中安裝兩個測力 儀來進行。3）最后一個階段是調(diào)查切向測力儀在工作條件下的性能，以及研究如何通 過改變安裝方法來改善測力儀的性能。這通過在處于工作條件下的巷道中形成的 混凝土板中安裝切向測力儀來實現(xiàn)。用于實驗的弦式汞測力儀都質(zhì)優(yōu)價廉，而且測量范圍達到20兆帕（如圖3） 所有的應(yīng)力測量都通過制造商提供的溫度修正來進行計算。校準實驗的第二階段是研究切向測力儀在理想和現(xiàn)實條件下的性能。在這個實驗中，將兩個測力儀嵌入拌好的混凝土板中，這個板高1.0米，寬1.0米，厚0.3米。兩個測力儀被綁定到一個用鋼筋加固的網(wǎng)格籠中，這個籠和希思羅機場 4號站隧道中所使用的是完全相同的。實驗設(shè)置如圖4所示，只是在第一組實驗中使用了兩個原裝的測力儀。本文稍后會介紹，